Re: Association lists

["Nic Ferrier" <nferrier at tapsellferrier dot co dot uk>]

>>> "Brian D. Carlstrom" <bdc@zurich.ai.mit.edu> 22-Jun-00 7:13:12 PM
>>>

>Associative arrays are not hashtables, although they 
>have a similar API, because their performance is not 
>equivilent

I appreciate that.

But it's as near as dammit because an assoc-list is only an
assoc-list whilst it has associaton pairs on it. It wouldn't be a
problem (from the user's point of view) to optimize it into a
hashtable within the compiler or interpreter.

This, it seems to me, would be the Scheme way - expressive and
minimalist but with hidden, implementation driven,  power (a la
loops).


>I think most Scheme implementations provide real hashs 
>as a seperate non-standard extensions. I know scheme 
>48 does, and my personal scheme in java just allows 
>people to use Java Hashtables.

Which of course I can also do quite easily with Kawa.

But, like loops, Scheme cannot do hashes (not easily anyway) so I
would have thought the  "schemey" thing to do is optimize assoc
lists?


>I don't think the compiler can lexically determine the 
>usage of a hash to see that it is never used as a list.

Perhaps not...

but the list itself could do that (as specified in my original
mail).

In fact I am actively considering doing it (though perhaps for now
I'll just deal with a hash using Java calls).


Nic